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Topic Title: Cable sizing
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Created On: 17 April 2018 06:07 AM
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 17 April 2018 06:07 AM
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callumcox

Posts: 10
Joined: 10 April 2018

Hi we are having a discussion on site about cable sizing for some machines,it's been years since I've done cable calcs but had a go last night. The machines are being fed from a mccb panel board 400amp mccbs for each one,the connection to the machine is a switched fused isolator containing 400amp fuses. The manufacturer has told us the machines start at 250amps due to the heating elements and motors but drop down to 100amps within half hour, The Swa cable is clipped to a ladder rack. The longest run is 40 mtrs. I calculated a 240mm cable,but been reading about lsf cable can carry more current. Using this type of cable 90c thermosetting allows a 120mm to be used, Am I doing something wrong to get to this size?. T.I.A
 17 April 2018 07:09 AM
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alanblaby

Posts: 795
Joined: 09 March 2012

If the connections at both ends are capable of taking the 90 degrees, then, yes, you can specify Thermosetting cable.
However. you still need to rate the cable to make sure it doesnt get too much current through it. - Why not reduce the fuse size? You only need 250 amps, so put suitable fuses in, then you can put in a smaller cable and all will comply.
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